1. Technical Field
The present invention relates to a liquid jet head for ejecting and recording droplets on a recording medium, and a liquid jet apparatus using this liquid jet head.
2. Related Art
In recent years, there has been utilized an ink jet type liquid jet head for ejecting ink droplets on a recording paper or the like and recording characters or graphics, or an ink jet type liquid jet head for ejecting a liquid material on a surface of an element substrate and forming a functional thin film. In this system, liquid such as ink or a liquid material is guided to a channel from a liquid tank via a supply tube, a pressure is applied to the liquid filling the channel, and the liquid is ejected from a nozzle communicated with the channel. When the liquid is ejected, the liquid jet head or the recording medium is moved and characters or graphics are recorded, or a functional thin film having a predetermined configuration is formed.
FIGS. 8A and 8B are schematic cross-sectional views of a liquid jet head 101 described in JP 2011-104791 A. FIG. 8A is a schematic longitudinal cross-sectional view of a groove 105 for generating a pressure wave in liquid, and FIG. 8B is a schematic cross-sectional view of the groove 105 in a direction orthogonal thereto. The liquid jet head 101 has a laminate structure including a piezoelectric plate 104 formed of a piezoelectric body, a cover plate 108 adhered to one surface of the piezoelectric plate 104, a flow path member 111 adhered onto the cover plate 108, and a nozzle plate 102 adhered to another surface of the piezoelectric plate 104. A deep groove 105a and a shallow groove 105b, which form the groove 105, are alternately formed in parallel on the piezoelectric plate 104. The deep groove 105a penetrates from the one surface to the other surface of the piezoelectric plate 104. The shallow groove 105b opens on the one surface of the piezoelectric plate 104, and a piezoelectric material is left on the other surface thereof. Side walls 106a to 106c are formed between the deep groove 105a and the shallow groove 105b. Drive electrodes 116a or 116c are formed on side surfaces of the deep groove 105a, and drive electrodes 116b or 116d are formed on side surfaces of the shallow groove 105b.
The cover plate 108 is provided with a liquid supply port 109 and a liquid discharge port 110. The liquid supply port 109 communicates with one end portion of the deep groove 105a, and the liquid discharge port 110 communicates with another end portion thereof. The flow path member 111 is provided with a liquid supply chamber 112 and a liquid discharge chamber 113. The liquid supply chamber 112 communicates with the liquid supply port 109, and the liquid discharge chamber 113 communicates with the liquid discharge port 110. The nozzle plate 102 is provided with a nozzle 103, and the nozzle 103 communicates with the deep groove 105a. 
This liquid jet head 101 is driven as follows. Liquid supplied through a supply joint 114 provided at the flow path member 111 fills the deep groove 105a via the liquid supply chamber 112 and the liquid supply port 109. Further, the liquid filling the deep groove 105a is discharged from a discharge joint 115 via the liquid discharge port 110 and the liquid discharge chamber 113 to the outside. Then, a potential difference is generated between the drive electrodes 116c and 116b and between the drive electrodes 116c and 116d. Accordingly, the side walls 106b and 106c are deformed in a thickness-shear mode, generating a pressure wave in the deep groove 105a. As a result, droplets are ejected from the nozzle 103.
In the liquid jet head 101 described in JP 2011-104791 A, the deep groove 105a for ejecting droplets and the shallow groove 105b for not ejecting droplets are alternately formed. The shallow groove 105b does not open on the nozzle plate 102 side of the piezoelectric plate 104, and the deep groove 105a opens on the nozzle plate 102 side thereof. The deep groove 105a and the shallow groove 105b are formed using a dicing blade (also referred to as “diamond cutter”) in which abrasive grains of, for example, diamond are embedded in an outer peripheral portion of a disk. As a result, as illustrated in FIG. 8A, an outer configuration of the dicing blade is transferred to both end portions of the groove 105. Normally, the dicing blade having a diameter of 2 inches or more is used. For example, when a depth of the deep groove 105a is 360 μm, a depth of the shallow groove 105b is 320 μm, and the piezoelectric plate 104 of 40 μm is left at a bottom portion of the shallow groove 105b, a circular configuration having a total of about 8 mm is formed at the both end portions of the shallow groove 105b in a longitudinal direction thereof. The circular configuration at the end portions of the shallow groove 105b is an unnecessary area. If this length can be shortened, the liquid jet head 101 can be made small and the number of the liquid jet heads 101 that can be taken from a piezoelectric wafer can be increased.
Therefore, if the piezoelectric plate 104 is not left on the bottom surface of the shallow groove 105b and the shallow groove 105b penetrates the piezoelectric plate 104 as with the deep groove 105a, the groove 105 having a short longitudinal length can be formed. As a result, the liquid jet head 101 is miniaturized and the number of the liquid jet heads 101 that can be taken from the piezoelectric wafer increases.
FIG. 9 is a schematic plan view of the piezoelectric plate 104 before the nozzle plate 102 is adhered thereto, as viewed from a side opposite to the cover plate 108 (see FIGS. 8A and 8B). In manufacturing process steps of the liquid jet head 101, the grooves 105 are formed in the piezoelectric plate 104, and then the cover plate 108 and the flow path member 111 are adhered to the piezoelectric plate 104 on the side where the grooves 105 have been formed. Next, the grooves 105 are caused to penetrate by grinding a surface of the piezoelectric plate 104 on a side opposite to the cover plate 108, and then the nozzle plate 102 is adhered to the surface of the piezoelectric plate 104 on the side opposite to the cover plate 108. Accordingly, the nozzle plate 102, in which the nozzle 103 has been previously formed, is adhered to a surface illustrated in FIG. 9. Alternatively, the nozzle 103 is opened by being irradiated with a laser beam after the nozzle plate 102 has been adhered to the surface. However, since 100 or more grooves 105 having the same configuration and having narrow pitches of 80 μm to 200 μm in an array direction are formed, it is difficult to distinguish the ejection groove 105 (the deep groove 105a in FIGS. 8A and 8B) from the non-ejection groove 105 (the shallow groove 105b in FIGS. 8A and 8B).